1. Field of the Invention
The present invention generally relates to the fabrication of microfuses within a semiconductor structure and, more specifically, to the structure and process of fabricating a SiCr microfuse within an integrated circuit (IC) which would be deletable by either a low voltage electrical pulse or a laser pulse. Such fuses are typically used for rerouting the various components of the IC, especially where redundancy in array structures is implemented.
2. Description of the Prior Art
Microfuses have been receiving considerable attention and gaining popularity in ultra large scale integrated (ULSI) circuit fabrication for implementing redundancy, particularly in the areas of bipolar and complementary metal oxide semiconductor (BICMOS) field effect transistor (FET) semiconductor chip manufacturing. Conventional microfuses presently used in the industry are deletable only by laser, and no electrical blowable microfuses integrated within ULSI circuits are known to exist.
In the early stages of SiCr fuse development work, a SiCr resistor fabrication process was used for the SiCr fuse fabrication, but major difficulties arose in using this approach. In the resistor fabrication process, Al was used as the mask for the reactive ion etching (RIE) step of the SiCr in a batch reactor. In transferring this resistor fabrication process to a fuse fabrication process, in which single wafer RIE systems are used, defects were observed in the Al mask that were replicated in the SiCr. These defects appeared to be caused by electrical discharge in the single-wafer RIE system. In the resistor fabrication program, the final metal layer (LM) was wet etched. Wet Al etchant does not attack SiCr, and no provision is needed to protect SiCr during etching of the LM layer. This particular fabrication method requires delineation of LM by RIE in a chlorinated plasma which attacks SiCr; therefore, an etch stop layer is added to the fuse material stack to protect the SiCr during the final stage of LM RIE. Another major shortcoming of the resistor-like process that uses an Al etch mask is that, for some unknown reason, cones of residual Al-based metal were left routinely adjacent to the SiCr fuses if LM is etched by RIE, but none were seen in the sub-etched area when this particular fabrication process is used to fabricate the SiCr fuses.
The major deficiencies encountered in the prior art are that the known microfuses are deletable only by laser pulses, and in the fabrication process, damage to the AL mask invariably occurs during the RIE step and residual metal (Al) remains next to the fuse.